Protective circuit for pressure charging of natural gas and the like

ABSTRACT

A protective fluid circuit is in fluid circuit with the highpressure side of a compressor for natural gas and controls the energization of the power source for the compressor such that when there is a drop in the pressure on this side, as when there is a leak, the compressor is inactivated. The protective circuit includes a check valve which opens when the pressure upstream of the valve is slightly more than the pressure downstream of the valve, the upstream side of the check valve being in pressure communication with the high-pressure side of the compressor. A pressure-sensitive switch of the balanced-pressure-type is in parallel fluid circuit with the check valve, with the outlet of the valve providing one source of pressure and the inlet of the valve providing the other source of pressure. The pressuresensitive switch controls a switching element in the circuit to the compressor&#39;&#39;s power source that when the valve closes, the switching element opens the circuit to the power source to inactivate the compressor. For starting the compressor, a selectively actuatable bypass valve is disposed across the pressure-sensitive switch to supply compressor pressure on both sides of the switch and prevent it from opening the circuit to the compressor power source.

United States Patent llll 3,623,827

[72] Inventor Robert W. McJones Primary Examiner-Carlton R. Croyle 529 Via Del Monte, Palos Verdes Estates. Assistant Examiner-Richard J. Sher Calif. 90274 Attorney-Christie. Parker & Hale [21] Appl. No. 19,903 {22] Filed Mar. l6, 1970 [45] patented No 30, 1971 ABSTRACT: A protective fluid circuit is in fluid circuit with the high-pressure side of a compressor for natural gas and controls the energization of the power source for the compressor such that when there is a drop in the pressure on this side. as when there is a leak. the compressor is inactivated. The protective circuit includes a check valve which opens when the pressure upstream of the valve is slightly more than the press- [54] PRoTECTlvE CIRCUIT FOR PRESSURE sure downstream of the valve, the upstream side of the check CHARGING OF NATURAL GAS AND TEE LIKE valve being in pressure communication with the high-pressure 4Chims2Dl-awing Figs. side of the compressor. A pressure-sensitive switch of the balanced-'pressure-type is in parallel fluid circuit with the [52] U.S. Cl 417/9, check vim/e mm the outlet of the valve providing one Source 73/40'5'73/49-L l37/456- l37/46o4l7/44 of pressure and the inlet of the valve providing the other [51] lnt.Cl F04b 49/10 source f pressure The pressure sensitive Switch Comm 3 [50] Field ofSearch 417/9. 38. Switching e|emem in the d m to he compressor-S power 44; 137/456'460i 84/6 Din/49'1- source that when the valve closes the switching element [56] References Cited opens the circuit to the power source to inactivate the compressor. For starting the compressor, a selectively actuatable UNITED STATES PATENTS bypass valve is disposed across the pressure-sensitive switch to 3,089,5l2 5/1963 Julien 137/460 supply compressor pressure on both sides of the switch and 3,184,958 5/l965 Eaton.. 4l7/9 X prevent it from opening the circuit to the compressor power 3,4l6,560 l2/l968 Bruno 137/456 source.

QOMQCE 0F Min/e44 64$ LL 0 C /2 g a J'OMflfiA-fi'flflfi 1 i 7 a $24 L50 I #22 /0 PROTECTIVE CIRCUIT FOR PRESSURE CHARGING OF NATURAL GAS AND THE LIKE BACKGROUND OF THE INVENTION The present invention relates to protective fluid circuits in general and, specifically, to a protective fluid circuit for use in conjunction with a compressor for natural gas and the like.

Compressors are used to fill tanks or bottles with natural gas at, say, 2,250 psi. pressure. The compressors are driven by various power sources such as an internal combustion engine or an electric motor. Typically, the high-pressure outlet of the compressor feeds a distribution line leading to one or more stations where the bottles are to be charged. Charging normally occurs without close supervision. In the event of a failure on the high-pressure side of a compressor, say in the compressors distribution line or in the fluid coupling between the line and a bottle, natural gas will escape to atmosphere. Obviously when such a failure occurs a severe safety hazard is present.

Thus there is a need for a protective device to shut down the compressor in the event of failure of the pressure integrity in the high-pressure distribution side of the compressor.

SUMMARY OF THE INVENTION The present invention provides a protective circuit to terminate compressor action in the event of loss of distribution pressure occasioned by, for example, a leak in the distribution circuit.

In one form the present invention contemplates a check valve adapted for fluid pressure communication with the discharge side of the compressor. The check valve is disposed to open when the pressure on the discharge side of the compressor is slightly greater than the pressure on the downstream side of the valve. A pressure-sensitive switch of the balancedpressure-type is also provided. One side of this switch is in fluid circuit with the check valve for sensing the pressure on the downstream side of the check valve. The other side of the switch is adapted for pressure communication with the discharge side of the compressor. The pressure-sensitive switch has means which is responsive to the closing of the check valve and the resulting imbalance of the switch to inactivate the compressor, the check valve closing in response to a drop of discharge side pressure below the pressure downstream of the check valve.

In preferred form, the present invention contemplates the use of a bypass valve for bypassing the check valve during the startup portion of a compressing cycle. The bypass valve is used in conjunction with the balanced-pressure-type pressuresensitive switch to supply discharge side compressor pressure to both of its sides to keep the switch from inactivating the compressor's power source. The bypass valve means, then, equalizes the pressure on both sides of the pressure-sensitive switch.

Another form of the present invention contemplates the protective circuit just described in combination with the compressor, the means for powering the compressor, and the distribution line means for supplying or distributing compressed gas to one or more desired points.

These and other features, aspects and advantages of the present invention will become more apparent from the following description, appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the protective circuit of the present invention in circuit with a compressor and its distribution circuit together with an electrical schematic of the power source of the compressor; and

FIG. 2 is a plot of discharge side pressure and pressure downstream of the check valve versus time to illustrate the principles of the present invention.

LII

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, the protective circuit is indicated in general by reference numeral 10. It is used in conjunction with a compressor 12in fluid circuit with a distribution line 14 from the high-pressure side of the compressor. The compressor is powered by an electric motor 16 which in turn is coupled through an electric circuit 18 to a source of electrical power 20.

Pressure-sensitive switch means in the form of a switch 22 of protective circuit 10 is coupled with circuit 18 for motor 16 for the opening and closing of a normally open switching element 24.

It should be understood that various means may be used to power the compressor other than the electric motor shown. For example, a spark-ignition internal combustion engine fueled by, for example, natural gas may be used. In the latter event, pressure-sensitive switch 22 will control a switching element in the ignition circuit of the internal combustion engine. Another alternative power source for the compressor is a diesel engine. In this event, the pressure-sensitive switch would be used to control, for example, a solenoid valve in the fuel line of the diesel engine.

The distribution circuit illustrated includes line 14 emanating from the high pressure side of the compressor for receiving compressed natural gas. At various points along the line, dis tribution points are located. At these distribution points, manually actuated valves 25, 26 and 28 may be disposed between line 14 and the items to be charged with natural gas, for example, bottles 30, 32 and 34, respectively. Check valves 36, 38 and 40 between each of the bottles 30, 32 and 34, and their associated valves 25, 26 and 28 provide means for preventing loss in pressure in the bottles when the pressure in line 14 falls.

Protective circuit 10 is in pressure communication with line 14 as through a tee 42. A line 44 extends from the tee to the upstream side of a check valve 46. The downstream side of check valve 46 is connected in fluid circuit to a line 48.

Pressure-sensitive switch 22.is in parallel fluid circuit with check valve 46 through lines 48 and 50. On either side of the pressure-sensitive switch are chambers 54 and 56 separated by a diaphragm or piston 58. A spring 60 is disposed in chamber 54 for biasing the piston to the right in the Figure. When the pressure in chamber 54 is sufficiently lower than the pressure in chamber 56, the piston moves to the left and through linkage (not shown) opens switching element 24 to open the circuit to motor 16.

A selectively actuatable, manually operated bypass valve 62 is also disposed in parallel fluid circuit with pressure-sensitive switch 22 to provide compressor pressure within both chambers of the pressure-sensitive switch, notwithstanding the fact that check valve 46 may be close. Line 64 provides this parallel connection for valve 62.

Electric circuit 18, except for switching element 24, is standard and supplies current to the armature and field windings of motor 16. The circuit includes an on-off switch 66.

In operation, bottles 30, 32 and 34 are connected in fluid circuit with line 14 through valves 25, 26 and 28, respectively. The valves are then turned on. Bypass valve 62 is opened to provide distribution line pressures in both chambers of pressure-sensitive switch 22. The compressor is then actuated by the closing of circuit 18 through on-off switch 66. Once the compressor is running, the pressure in line 14 will be sensed in both chambers of pressure sensitive switch 22 and check valve 46 will be open. As a consequence, switching element 24 will be closed and the circuit to motor 16 maintained without valve 62 being open. At this point, manually actuated bypass valve 62 is closed to activate protective circuit 10 by pressure communication between chamber 56 and the outlet of check valve 46.

In the event that there is no loss of pressure in the distribution system, the compressor will operate until bottles 30 through 34 are brought up to the desired pressure of, say, 2,250 p.s.i.

In the event, however, that there is a pressure failure, as for example in the coupling between check valve 36 and valve 25, the protective circuit will open the circuit of motor 16 and the compressor will be shut down.

The operation of the protective fluid circuit when there is a pressure failure is as follows. With the drop of pressure in line 14, check valve 46 will close because the pressure in line 48 will be higher than the pressure in line 44 by a small amount. Manually actuated valve 62 has previously been closed. Thus, the pressure in chamber 54 will drop relative to the pressure in chamber 56. Very soon the pressure in chamber 56 will overcome the combined effects of spring 60 and the line pressure in chamber 54 to move piston 58 to the left in the Figure. This movement causes switching element 24 to open. With the opening of switching element 24, the circuit to motor 16 is no longer complete and the motor and its driven compressor are shut down.

The operation of the protective circuit can be visualized with the aid of FIG. 2. In this Figure, the solid line represents pressure upstream of check valve 46 while the dashed line represents pressure downstream of the valve. During charging, the two pressures closely parallel each other, with the pressure downstream of the check valve being slightly less than the pressure upstream. When there is a leak on the upstream side of the check valve, however, the pressure on the downstream side of the valve very soon exceeds the pressure on the upstream side and the valve closes. Once check valve 46 closes, the pressure-sensitive switch opens switching element 24 to turn off compressor motor 16.

In the event that an additional bottle is to be charged during the charging of bottles 30 through 34, the new bottle is connected to line 14. The pressure in the line will therefore drop. Therefore, valve 62 is opened before the new bottle is connected into line 14 to maintain compressor 12 on the line. Once the new bottle has been connected, valve 62 is closed. The pressure history in line 14 will then be as it is shown in FIG. 2 to the right of the discontinuity. The pressure in the line will rapidly increase until the new bottle is up to the pressure of bottles 30, 32 and 34. Thereafter the charging rate of the bottles will be slower than before because of the presence of the additional bottle.

The protective circuit of the present invention, then, offers a simple and expedient way of preventing potentially disastrous conditions which would otherwise be occasioned by the escape of natural gas from the distribution side of the compressor occasioned by leak or failure.

The present invention has been described with reference to a preferred embodiment. The spirit and scope of the appended claims should not, however, necessarily be limited to the foregoing description.

. What is claimed is:

1. A protective fluid circuit for pressure-charging systems comprising: 1

a. a check valve adapted for fluid communication with the discharge side of a compressor such that it closes when the pressure on the discharge side of the compressor is less than the pressure on the downstream side of the check valve; and

b. a pressure-sensitive switch of the balanced-pressure-type having one side in closed fluid circuit with the check valve on the downstream side thereof, the other side of the pressure-sensitive switch being adapted for fluid pressure communication with the discharge side of the compressor, the pressure-sensitive switch having means responsive to the closing of the check valve to inactivate the compressor.

2. The protective fluid circuit claimed in claim 1 including:

a selectively actuatable bypass valve in parallel fluid circuit with the pressure-sensitive switch for supplying discharge side compressor pressure in place of the pressure on the downstream side of the check valve to the pressure-sensitive switch to prevent inactivation of the compressor.

3. A charging circuit for a gas such as natural gas comprisa a compressor adapted to compress the gas from a source thereof;

b. means for powering the compressor;

c. distribution line means for supplying compressed gas to a desired point; and

d. a protective circuit for inactivating the powering means when there is a pressure drop in the distribution line means which includes:

i. a check valve in fluid circuit with the distribution line means such that it closes when the pressure in the line means is less than the pressure on the downstream side of the check valve; and

a pressure-sensitive switch of the balanced-pressuretype having one side in closed fluid circuit with the check valve on the downstream side thereof and its other side in closed fluid circuit with the distribution line means, the pressure-sensitive switch having means to inactivate the powering means upon the closing of the check valve in response to a drop in pressure in the distribution line means.

4. The charging circuit claimed in claim 3 including:

a selectively actuatable bypass valve in parallel fluid circuit with the pressure-sensitive switch for supplying distribution line pressure in place of the pressure on the downstream side of the check valve to the pressure-sensitive switch to prevent inactivation of the compressor. 

2. The protective fluid circuit claimed in claim 1 including: a selectively actuatable bypass valve in parallel fluid circuit with the pressure-sensitive switch for supplying discharge side compressor pressure in place of the pressure on the downstream side of the check valve to the pressure-sensitive switch to prevent inactivation of the compressor.
 3. A charging circuit for a gas such as natural gas comprising: a. a compressor adapted to compress the gas from a source thereof; b. means for powering the compressor; c. distribution line means for supplying compressed gas to a desired point; and d. a protective circuit for inactivating the powering means when there is a pressure drop in the distribution line means which includes: i. a check valve in fluid circuit with the distribution line means such that it closes when the pressure in the line means is less than the pressure on the downstream side of the check valve; and ii. a pressure-sensitive switch of the balanced-pressure-type having one side in closed fluid circuit with the check valve on the downstream side thereof and its other side in closed fluid circuit with the distribution line means, the pressure-sensitive switch having means to inactivate the powering means upon the closing of the check valve in response to a drop in pressure in the distribution line means.
 4. The charging circuit claimed in claim 3 including: a selectively actuatable bypass valve in parallel fluid circuit with the pressure-sensitive switch for supplying distribution line pressure in place of the pressure on the downstream side of the check valve to the pressure-sensitive switch to prevent inactivation of the compressor. 